The rushing sound grew louder as Ian Joughin walked toward it, over ice smoothed by tons of flowing water that dropped out of sight through 20-foot diameter hole. He stopped 10 feet away from the hole’s ice-crusted lip, then shuffled carefully forward to peer inside, watching water fall past an edge of ice crystals. Ten feet below, the ice shone a tropical blue that seemed almost surreal surrounded by all this ice and snow, the way a camel would seem out of place on this ice sheet if it suddenly galloped past.

His eyes followed the falling water until they met darkness.

“That water is going a half mile down, all the way to the bedrock, and it’s a one way ticket,” he said, shouting over the sound of the falling water.

Yesterday, when scientists walked to this full lake basin, it contained enough melted water to fill about 2,000 Olympic sized swimming pools. Much of it drained sometime this morning, in about six hours.